The heat exchangers for use in the air conditioning system generally comprise coolant pipes which extend from a heat exchanger body, wherein each coolant pipe has at its end a pipe joint to be connected to an external pipings.
Usually, the coolant pipes are seam-welded pipes which are made from an aluminum brazing sheet having its outer surface clad with a brazing agent layer. In such a case, the pipe joint has heretofore been adjoined to the coolant pipe in such a manner that the end thereof is forcibly inserted into a pipe receiving hole of the joint so as to be self-retained therein. In the subsequent brazing process, the brazing agent layer clad on the pipe outer surface is utilized to make the coolant pipe integral with the pipe joint.
It has however been a problem that the coolant pipe adjoined to the pipe joint is expensive if it is a clad pipe such as the seam welded pipe made of the brazing sheet, thus raising the manufacture cost of the heat exchanger. This problem would be serious where the coolant pipe has to be excessively long due to a certain arrangement of the external pipings.
Recently, a bare pipe 51 which is not clad with any brazing agent was therefore proposed for use as the coolant pipe in an improved junction as shown in FIG. 10. The bare pipe is for example an inexpensive extruded aluminum pipe having a beaded portion 52. An end of the pipe 51 is put into a pipe receiving bore 55 formed in a pipe joint 53, with a brazing agent ring 54 being sandwiched between the beaded portion 52 and the joint 53, before brazed one to another in this state.
Since the end of the pipe 51 is tightly forced into the bore 55 of the joint 53, they can stand immovable relative to each other in a temporary assembly even if the brazing agent ring 54 would be missed. Consequently, the temporary assemblies devoid of the brazing agent ring 54 have occasionally been subjected to the brazing process within an oven, causing an incompletely brazed product. In addition, a flux covering the adjoined portion of the product taken out of the oven makes it difficult to judge whether the brazing is complete or not. Further, since the flux per se does behave as a poor agent to braze the adjacent members, there is a possibility that an incompletely brazed product erroneously passes the following leak test.
In view of the problems inherent in the prior art heat exchangers, an object of the present invention is to provide a heat exchanger which comprises a heat exchanger body, connection pipes each extending therefrom for flowing a heat exchanging medium, and a pipe joint attached to at least one of external pipings, wherein the pipe joint is affixed securely and inexpensively to one of the connection pipes.